Lens tissue has been shown to contain several degradative enzymes, however, these enzymes do not function in normal lens due to the presence of specific protein inhibitors. Since macromolecular breakdown products increase in cataractous lenses, we have proposed that the cataractogenic process involves the inactivation of these endogenous inhibitors, causing the release of hydrolytic enzymes. We have demonstrated two trypsin inhibitors and at least one trypsin-like enzymes in bovine lens tissue. Purification of these inhibitors will hopefully permit the determination of the mechanism of actin of these inhibitors and test their susceptibility to various cataractogenic agents. Further characterization of the lens trypsin-like enzyme may allow us to study release of the proteinase from the proteinase-inhibitor complex. The ability of the various lens proteinase to hydrolyze lens crystallins will be demonstrated and the degraded peptides can be compared to peptides produced in the lens nucleus and during the cataractogenic process.